In the complex world of autoimmune disorders, biomarkers serve as crucial indicators of our body's internal state. These measurable substances in our blood and body fluids can reveal the inner workings of our immune system. Understanding autoimmune test results can offer valuable insights for both diagnosis and treatment.
ANA (Antinuclear Antibody) Test
What does an ANA test measure?
An ANA test measures the presence of antinuclear antibodies (ANA) in your blood. These are antibodies that target the nuclei of your body's own cells, which is a common feature in autoimmune disorders. The test is frequently used to help diagnose autoimmune conditions like systemic lupus erythematosus (SLE), Sjögren’s syndrome, scleroderma, and myositis.
ANA test positivity depends on sample dilution. Lower dilutions have more antibodies per fluid volume, while higher dilutions have fewer. As more fluid is added, antibody concentration decreases, affecting test results. For example, a 1:40 dilution may detect antibodies, but a 1:160 dilution might not. Thus, a positive result from a higher dilution is more reliable than one from a lower dilution.
What’s the difference between an ANA and an ENA test?
While the ANA test detects the general presence and quantity of antinuclear antibodies, the ENA (Extractable Nuclear Antigen) test identifies specific autoantibodies that are often found in autoimmune diseases. ENA testing is more exact–it’s used to differentiate between various conditions that may test positive on an ANA, like lupus, scleroderma, and mixed connective tissue disease. The ENA test differentiates between antibodies by extracting them from the cell’s nucleus to reveal the type of blood protein they’re attached to.
What factors affect ANA?
- Age: ANA levels tend to increase with age, even in healthy individuals. About a third of adults over 65 can test positive for antinuclear antibodies.
- Sex: Women are also at higher risk for testing positive for ANA without having an autoimmune disorder.
- Infections (often viral): Viral infections are likely to cause patients to test positive on an ANA test, but only temporarily.
- Autoimmune diseases: Certain autoimmune conditions occur because of ANAs, such as systemic lupus erythematosus (SLE), rheumatoid arthritis, Sjogren’s, scleroderma, Addison disease, and autoimmune hepatitis.
What’s the reference range for ANA?
A normal ANA test result is typically negative, meaning no antinuclear antibodies are detected.
A positive ANA result does not always confirm an autoimmune disease but may indicate the need for further testing based on the patient’s symptoms and medical history.
ESR (Erythrocyte Sedimentation Rate) Test
What does an ESR test measure?
Erythrocyte sedimentation rate measures how much your red blood cells stick together. The test works by measuring how fast your red blood cells sink to the bottom of a test tube. If the clump sinks quickly (a higher ESR rate), this indicates that it's larger and could be a sign of inflammation and an underlying condition.
This test is used to monitor and diagnose medical conditions that cause inflammation, like arthritis, inflammatory bowel disease, and infection. Symptoms like headaches, joint stiffness, unexplainable fevers, and anemia may cause your doctor to recommend this test.
What factors affect ESR?
The factors that can affect ESR results are:
- Inflammation: High levels of inflammation can increase ESR due to increased clumping of red blood cells.
- Pregnancy and menstruation: Hormonal changes during these periods can cause a temporary increase in ESR levels.
- Anemia: Low red blood cell count can affect the sedimentation rate, often leading to higher ESR values.
- Advancing age: ESR tends to increase naturally as people get older, possibly due to age-related changes in red blood cell composition.
- Medications: Certain medications can lower ESR, such as statins or NSAIDs.
What is the reference range for ESR levels depending on age?
The reference ranges for ESR by age are:
Men- Under 50 years: ≤15 mm/hr
- Over 50 years: ≤20 mm/hr
- Under 50 years: ≤ 20 mm/hr
- Over 50 years old: ≤30 mm/hr
Children: ≤10 mm/hr
C-reactive Protein (CRP) Test
What does a CRP test measure?
C-reactive protein (CRP) is an inflammatory protein that can increase dramatically at sites of infection or inflammation.
What factors can affect C-reactive Protein?
- Infection: Elevated levels of CRP in your blood often indicate that your immune system is fighting a pathogen or responding to some sort of trauma. CRP is one of the most common signs of infection.
- Inflammation: There’s a wide variety of potential causes for inflammation, so elevated levels of CRP between 1 and 10 mg/dL can be difficult to interpret accurately.
- Smoking Status: Smoking cigarettes has been shown to increase inflammation in your body.
- Diet: There is strong evidence that a diet high in vegetables, fruits, legumes, grains, fish, and unsaturated fats can help lower your CRP levels. Diets high in whole grains and low in refined grains have also been shown to lower CRP levels.
- Heart Disease: Consistently elevated CRP levels are associated with a greater risk of heart disease, but one abnormal test result is not necessarily a cause for concern.
- Medications: Certain anti-inflammatory medications, like prednisone, a glucocorticoid, can lower CRP levels.
What’s the reference range for CRP?
The reference ranges for CRP are as follows:
- Less than 3 mg/L is considered within the normal range for CRP and is seen in most healthy adults.
- 3 to 10 mg/L indicates normal or minor elevation of CRP, which can be seen in obesity, pregnancy, depression, diabetes, common cold, gingivitis, periodontitis, sedentary lifestyle, cigarette smoking, and genetic polymorphisms.
- 10.0 to 100.0 mg/L indicates moderate CRP elevation. This is common in patients with systemic inflammation with conditions like RA, SLE, or other autoimmune diseases, malignancies, myocardial infarction, pancreatitis, or bronchitis.
- More than 100.0 mg/L indicates a marked elevation of CRP, which is seen in severe bacterial infections, viral infections, systemic vasculitis, bone infections (osteomyelitis), or major trauma.
- CRP levels aren’t considered dangerous until they reach 500 mg/L or above, which is most commonly associated with severe infection.
Immunoglobulin A Test
What does an immunoglobulin A test measure?
Immunoglobulin A (IgA) tests measure the relative amount of IgA antibodies in your body, which are produced by your immune system to protect against foreign invaders. IgA works by binding to antigens and preventing entry into the body’s mucus and circulatory system.
People who are deficient in IgA are more likely to experience lung and gastrointestinal infections due to the lack of protection from foreign antigens in mucosal layers.
What factors affect immunoglobulin A levels?
- Infection: Higher immunoglobulin A can occur when the immune system is actively fighting off infection.
- Autoimmune conditions: High IgA levels can also occur in patients suffering from autoimmune conditions, like lupus, rheumatoid arthritis, or celiac disease, which results from ‘self-antibodies’ attacking the digestive tract. Celiac disease, however, always requires further antibody testing to confirm a diagnosis.
- Medications: Some medications, like immunosuppressants used for surgery, certain antibacterial agents, and anti-seizure drugs, can cause lower levels of IgA, but their effects are easily reversed once patients stop taking them.
- Viral infections: Certain viral infections like Hepatitis C, Epstein-Barr, and Rubella can cause IgA deficiencies.
What is the reference range for IgA?
The normal reference range for Immunoglobulin A (IgA) in serum typically falls between 0.7 to 4.0 g/L for adults, though this can vary slightly depending on the laboratory and population being tested.
Rheumatoid Factor (RF) Test
What does an RF test measure?
The rheumatoid factor test measures the presence and levels of rheumatoid factor, an autoantibody that targets the body’s own tissues, particularly the antibody immunoglobulin M (IgM). High RF levels are commonly associated with autoimmune diseases such as rheumatoid arthritis and Sjögren’s syndrome.
What factors affect RF levels?
- Autoimmune conditions: RF levels can be increased by autoimmune conditions like rheumatoid arthritis (RA), Sjögren’s syndrome, and lupus.
- Non-rheumatic disease: Chronic infections like hepatitis C and tuberculosis can increase RF levels as well due to prolonged inflammation.
- Age: RA is most commonly seen in females between the ages of 25-45, although it can affect all ages and sexes.
- Certain cancers: Some evidence has shown that high RF factors can be associated with the progression of certain cancers, like non-small cell lung cancer (NSCLC) and lymphoma.
What is the reference range for RF?
- The normal reference range for RF is typically less than 15 IU/mL, but this may vary slightly depending on the laboratory's standards.
- A concerning rheumatoid factor is a high RF level, often over 20 IU/mL, which could indicate the presence of autoimmune diseases such as rheumatoid arthritis, especially when accompanied by symptoms like joint pain and swelling.
Anti-Cyclic Citrullinated Peptide (Anti-CCP) Antibody Test
What does an Anti-CCP test measure?
Anti-CCP Antibody tests (ACPAs) measure the presence of antibodies that are common in patients with rheumatoid arthritis, or RA. This test is typically given alongside or after an RF test since it’s more specific and usually used to confirm a diagnosis. Anti-cyclic citrullinated peptide antibodies attack proteins that reside in the joint cavities of patients with RA due to inflammation.
What factors affect anti-CCP?
- Disease Onset: Anti-CCP antibodies are often detectable in the early stages of RA, sometimes even before symptoms manifest. However, they may not appear in all patients, and their levels can fluctuate.
- Other Conditions: While highly specific for RA, anti-CCP antibodies can occasionally be present in other conditions that can cause arthritis, such as lupus (SLE), psoriatic arthritis, or undifferentiated connective tissue diseases.
- Additional factors: Age and allergic conditions might lead to false positives.
What’s the reference range for Anti-CCP?
A positive result on an anti-CCP test indicates the presence of anti-CCP antibodies, which is often indicative of rheumatoid arthritis. According to a 2005 study on Korean patients with RA, the average level of anti-CCP antibodies was:
- 48.9 U/mL for RA patients
- 4.5 U/mL for patients with other rheumatic diseases
- 0.8 U/mL for healthy controls
The amount of anti-CCP antibodies varied greatly among individuals in each group, however, so exact reference ranges were not established.
Thyroid Antibodies
Thyroid antibody testing is common when screening for diseases like Hashimoto’s thyroiditis and Graves’ disease.
Antibody testing is usually performed after testing for primary thyroid dysfunction by looking at thyroid hormone levels like T3, T4, and TSH.
If your provider suspects your thyroid condition is due to autoimmune dysfunction, they’ll usually test:
-
Thyroid peroxidase antibodies (TPOAb) and Thyroglobulin antibodies (TgAb)
- High levels indicate hypothyroidism caused by Hashimoto’s.
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Thyrotropin receptor antibodies
- High levels can indicate hyperthyroidism caused by Graves’ disease.
